DESCRIPTION: The broad long range objective is to understand the role of cellular adhesion molecules in the biology of HIV. The hypothesis is that functional cell adhesion molecules acquired by the virus can independently mediate binding of virus to cells, increase the avidity of CD4 mediated virus binding, and change virus tropism. The project will focus on three adhesion molecules: LFA-1, VLA-4, and CD44. The specific aim are to: (a) Characterize the role of cell adhesion molecules in HIV transmission using expression vectors to change adhesion molecule phenotype of cells; (b) Evaluate the contribution of cell adhesion molecules to HIV tropism; (c) Characterize the effect of HIV infection on expression and function of adhesion molecules; (d) Determine if cell adhesion molecules are associated with HIV in vivo using plasma from MACS participants and well characterized plasmid HIV for acquired adhesion molecules; and (e) Define the role of LFA-1 in serum neutralization of HIV infection in primary T cells.